The invention relates to screens for material processing and in particular to a screen apparatus and method for sizing and separating particles of materials by motorized vibration of one or more screens. More particularly, the invention is directed to a material processing apparatus and method which enables efficient sizing and separation of particles of low-density materials.
Material sizing equipment commonly is used in a variety of industrial processes including mineral processing of coal, iron ore, kaolin, bauxite, taconite, gold, phosphate, potash, silica sand, aggregate, and limestone. Such sizing equipment also is useful in chemical processing, pulp and paper processing, food processing, waste water and sewage treatment, refuse processing, soil processing, oil well drilling fluid cleaning, and in processing low-density materials such as fertilizer and plastic pellets. Equipment of the type intended for sizing and separating particles of a material usually includes a stand, a frame movably suspended on the stand, one or more elongated screens of varying sizes, depending on the processing application, mounted on the frame, and one or more motors mounted on the frame for vibrating the frame and attached screen. The material typically is deposited on one end of the vibrating screen, which sizes and separates particles of the material as it moves along the screen. The screen can be disposed horizontally and parallel to the surface on which the sizing equipment rests, or it can be inclined relative thereto with the material to be sized being deposited on the upper or lower end of the screen. In certain applications, the screen also serves to separate water from the material being sized.
Although such sizing equipment typically performs its intended functions well, it has become apparent in applications involving the sizing of low density dry materials having particles ranging in size from about 2 mesh (12 millimeters) to about 325 mesh (45 microns), that existing sizing equipment does not achieve efficient separation of these types of materials. More specifically, most sizing equipment does not apply a combination generally circular planar motion to one end of the screen, and a generally oblong linear reciprocating planar motion to the opposite end of the screen and the central portion of the screen. Rather, other types of forces, such as those generated by non-planar gyratory motions applied to the screens, are utilized in many prior art sizing apparatus. While this type of gyratory motion, as well as other types of motions such as those that generate generally vertical forces, work satisfactorily for sizing particles of relatively higher density materials, such prior art known vibrating motions are not the most efficient motions for achieving separation of particles of lower density materials.
However, certain known prior art particle sizing equipment has been developed in an attempt to efficiently achieve sizing and separation of particles of low-density materials. Rotex Inc. utilizes equipment which applies a generally circular planar motion to only one end of its screen, while also generally reciprocating the central portion and the opposite end of the screen in an oblong linear motion and in the same direction as the line of travel of material along the screen. However, this motion is achieved by a relatively complex crankshaft gear and leaf spring arrangement of parts, rather than one or more vibratory motors, together with bouncing balls disposed beneath the sloped screen to control screen blinding or clogging, to achieve sizing and separation of particles of low density materials. Similarly, Great Western Manufacturing Company, Inc. also utilizes a non-vibratory drive system rather than a vibratory motor to apply a generally large circular motion to the entire screen to enable sizing and separation. However, such sizing equipment is relatively complicated and expensive to manufacture and maintain, and still does not achieve desired levels of sizing and separation of particles of low-density materials.
The present invention solves a long-felt need in the material sizing art of how to efficiently size and separate particles of relatively low-density materials, by utilizing a certain vibratory motor placement and elongated sizing frame and screen, together with an arrangement of a plurality of various suspension assemblies, to aid material movement on the screen in such a manner as to achieve efficient sizing and separation of particles of low-density materials in equipment which is cost efficient to manufacture and maintain.
Objectives of the present invention include providing a sizing apparatus and method which efficiently sizes and separates particles of low-density materials, while utilizing a traditional vibratory motor.
Another objective of the present invention is to provide such a sizing apparatus and method which is relatively simple, inexpensive, reliable and easy to use and maintain.
These objectives and advantages are obtained by the apparatus for sizing and separating particles of a material of the present invention, the apparatus including a stand, a frame, means attached to the stand and the frame for movably suspending the frame on the stand, an enclosure mounted on the frame, the enclosure having a material input end, a central portion and a material output end, at least one screen mounted in the enclosure, the screen being inclined downwardly in a direction from the enclosure input end to the enclosure output end, and a vibratory motor mounted on the frame, so that a generally circular planar motion is imparted to the frame, the enclosure and the screen at the enclosure input end, and a generally oblong linear reciprocating motion is imparted at the enclosure central portion and the output end.